Method for removing an electromagnetic module from an electrical machine

ABSTRACT

In a first aspect, a method for removing an electromagnetic module from an electrical machine is provided. The electrical machine comprises a plurality of electromagnetic modules having an electromagnetic material. The electromagnetic modules comprise base and a support extending from the base and supporting the electromagnetic material. The base comprises a bottom surface and a first side surface. The first side surface comprises an axially extending groove defining a cooling channel with an axially extending groove of a first side surface of an adjacent electromagnetic module. The method comprises inserting a rod in a cooling channel formed by the groove of the electromagnetic module to be removed and a groove of an adjacent electromagnetic module; releasing the electromagnetic module to be removed from a structure of the electrical machine; and sliding the electromagnetic module to be removed along the rod.

RELATED APPLICATION

The present application is a Divisional Application of U.S. applicationSer. No. 16/937,249, filed Jul. 23, 2020, which claims priority to EPApplication No. 19382641.9, filed Jul. 26, 2019, which are incorporatedby reference herein in their entirety.

The present disclosure relates to electromagnetic modules for electricalmachines having a cooling channel, and a method for removing anelectromagnetic module from an electrical machine.

BACKGROUND

Electrical machines, such as motors and generators, generally comprise arotor structure and a stator structure. Large electrical generators maybe permanent magnet generators (PMG) or electrically excited generators.

Such generators may be used for example in wind turbines, in particularin offshore wind turbines. Wind turbines generally comprise a rotor witha rotor hub and a plurality of blades. The rotor is set into rotationunder the influence of the wind on the blades. The rotation of the rotorshaft either directly drives the generator rotor (“directly driven”) orthrough the use of a gearbox. Such a direct drive wind turbine generatormay have e.g. a diameter of 6-10 meters (236-328 inches), a length ofe.g. 2-3 meters (79-118 inches) and may rotate at low speed, for examplein the range of 2 to 20 rpm (revolutions per minute). Alternatively,permanent magnet generators or electrically excited generators may alsobe coupled to a gearbox which increases the rotational speed of thegenerator to for example between 50 and 500 rpm or even more.

Electrical machines comprise a rotor which rotates with respect to thestator. The rotor may be the inner structure and the stator the outerstructure. The stator in this case thus surrounds the rotor.Alternatively, in some configurations it may be the opposite, i.e. therotor surrounds the stator.

In case of permanent magnet generators (PMG), permanent magnets (PM) aregenerally arranged on the rotor (although they could also be arrangedalternatively in the stator structure), whereas winding elements (e.g.coils) are usually included in the stator (although they couldalternatively be arranged on the rotor structure). Permanent magnetgenerators are generally deemed to be reliable and require lessmaintenance than other generator typologies.

Multiple permanent magnets may be provided in permanent magnet modules,which may be attached to the rotor as a single item. A permanent magnetmodule may be defined as a unit having a plurality of permanent magnets,such that the plurality of magnets can be mounted and unmountedtogether. Such a module may have a module base with a shape suitable forhousing or carrying a plurality of permanent magnets that may be fixedto the base. The base may be configured to be fixed to a rotor rim insuch a way that the plurality of magnets is fixed together to the rotorrim through the module base. The use of permanent magnet modules mayfacilitate the manufacturing of a rotor.

The stator may generally comprise electrical or stator windings. Statorwindings may be arranged in stator segments. A plurality of statorsegments may be connected to a stator rim along the statorcircumference. The stator segments may comprise a base configured to befixed to stator rim and a tooth protruding from the base receiving astator winding. A stator winding may be wound around the tooth. A statorsegment may comprise a plurality of teeth and a plurality of statorwindings wounded around each of the teeth. Accordingly, stator windingsmay be mounted and unmounted to or from the stator through the statorsegments. Using stator segments may facilitate the manufacturing of astator and the replacement of malfunctioning stator or electricalwindings.

The electromagnetic components of an electrical machine, e.g. permanentmagnet modules and stator windings, may be cooled to reduce heat lossessuch that the performance of the electrical machine may be optimized.Air cooling channels may be provided in the stator and/or the rotor tocool the electromagnetic components. For example, air cooling channelsmay be formed in permanent magnet modules or in stator segments.However, large air cooling channels may weaken the structural behaviorof the rotor or of the stator components.

Electromagnetic components, e.g. permanent magnet modules or statorsegments, may be deteriorated during its use and may have to be repairedor replaced by another one. Electromagnetic components may thus have tobe removed. However, electromagnetic components may be attracted byother electromagnetic components. For example, electromagneticcomponents associated with the stator are generally electromagneticallyattracted by the electromagnetic components associated with the rotor.Accordingly, removing an electromagnetic component from the electricalmachine may require counteracting the electromagnetic forces createdbetween the electromagnetic components. This may also occur when anelectromagnetic component is inserted in an electrical machine. Thesemanufacturing or maintenance operations may make more difficult thedesign of the electromagnetic components and also of the electricalmachine. This may specifically occur in electrical generators for directdrives wind turbines as the electromagnetic forces between the rotor andthe stator are large.

The size and type of electrical machines and the potential problemsdescribed herein are not limited to generators in direct drive offshoreapplications, and not even to the field of wind turbines only.Electrical machines of considerable dimensions that may suffer from thesame problems and/or have the same complications may also be found ine.g. steam turbines and water turbines.

The present disclosure provides examples of systems and methods that atleast partially resolve some of the aforementioned disadvantages.

SUMMARY

In one aspect, a method for removing an electromagnetic module from anelectrical machine having a rotor and a stator is provided. Theelectrical machine comprises a plurality of electromagnetic moduleshaving an electromagnetic material, the electromagnetic material beingone of a permanent magnet and a stator winding. The electromagneticmodules comprise base and a support extending from the base andsupporting the electromagnetic material. The base comprises a bottomsurface and a first side surface. The first side surface comprises anaxially extending groove defining a cooling channel with an axiallyextending groove of a first side surface of an adjacent electromagneticmodule. The method comprises inserting a rod in a cooling channel formedby the groove of the electromagnetic module to be removed and a grooveof an adjacent electromagnetic module; releasing the electromagneticmodule to be removed from a structure of the electrical machine; andsliding the electromagnetic module to be removed along the rod.

According to this aspect, the cooling channel formed by the grooves oftwo neighboring electromagnetic modules may be used for inserting a rodto counteract the electromagnetic forces inside the electrical machineacting on the electromagnetic module to be extracted. For example, ifthe electromagnetic module to be removed is a stator module, thepermanent magnets arranged at the rotor may attract the stator module.Electromagnetic forces may thus be created between electromagneticmodules arranged at the stator and electromagnetic modules arranged atthe rotor. The rod may be radially retained inside the groove of theadjacent electromagnetic module. The electromagnetic module to beremoved may slide along the rod in such a way that the rod retains ormaintains the radial position of the electromagnetic module. Radialdisplacements of the electromagnetic modules, for example from thestator to the rotor, may be prevented. Accordingly, a single channel hasboth functions: cooling the electromagnetic material and receiving a rodfor removing one electromagnetic module. Forming several channels in anelectromagnetic module with independent functions may thus be avoided.As a result, weakening the structural behavior of the electromagneticmodule may be prevented and a more compact electromagnetic module may beprovided. In addition, as less channels in the base of anelectromagnetic module are required, the magnetic flux through theelectromagnetic module may be optimized and the electrical efficiency ofthe electrical machine may be improved.

In a further aspect, a method for inserting an electromagnetic module inan electrical machine is provided. Then electrical machine comprises arotor, a stator and a plurality of electromagnetic modules having anelectromagnetic material. The electromagnetic material is one of apermanent magnet and a stator winding. The electromagnetic modulescomprise a base and a support extending from the base and supporting theelectromagnetic material. The base comprises a bottom surface and afirst side surface. The first side surface comprises an axiallyextending groove, the axially extending groove is configured to define acooling channel with an axially extending groove of a first side surfaceof an adjacent electromagnetic module. The method comprises inserting arod in the groove of an electromagnetic module attached to a structureof the electrical machine, inserting a portion of the rod in a portionof the groove of the electromagnetic module to be inserted, sliding theelectromagnetic module to be inserted along the rod to position theelectromagnetic module to be inserted adjacent to the electromagneticmodule attached to the structure of the electrical machine, andattaching the electromagnetic module to the structure of the electricalmachine.

According to this aspect, the cooling channel formed by the grooves oftwo neighboring electromagnetic modules may be used for inserting anelectromagnetic module in an electrical machine. Similar to removing anelectromagnetic module, the rod may radially retain the electromagneticmodule being inserted in the electrical machine.

In yet a further aspect, a stator segment is provided. The statorsegment comprises a base and a tooth protruding from the base receivinga stator winding. The base comprises a bottom surface and a first sidesurface having an axially extending groove. The groove comprises anupper surface and a lower surface. The groove is configured to form acooling channel with an axially extending groove of a first side surfaceof an adjacent stator segment. The cooling channel is further configuredto receive a rod for removing the stator segment from a stator rim andto cool the stator winding.

According to this aspect, the cooling channel may be used for coolingthe stator winding and for facilitating the extraction or insertion ofthe stator segment in an electrical machine. During the extraction orinsertion of the stator segment, a rod may be inserted in the coolingchannel formed by the groove of the stator segment to be removed and thegroove of an adjacent stator segment. Furthermore, as the coolingchannel is arranged close to the stator winding, the cooling may beimproved and the electrical efficiency of the electrical machine maythus be increased. Cooling channels commonly arranged in the stator coremay thus be avoided. Consequently, the size of the stator, andconsequently of the electrical machine, may be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples of the present disclosure will be described in thefollowing, with reference to the appended drawings, in which:

FIG. 1 illustrates a perspective view of a wind turbine according to oneexample of the present disclosure;

FIG. 2 illustrates a simplified, internal view of a nacelle of a windturbine according to one example of the present disclosure;

FIG. 3 schematically represents a cross-sectional view of two adjacentstator segments according to one example of the present disclosure;

FIG. 4 schematically represents removing a stator segment from a stator;

FIG. 5 schematically represents a cross-sectional view of a statorsegment according to one example of the present disclosure;

FIG. 6 schematically represents a cross-sectional view of a statorsegment according to another example of the present disclosure;

FIG. 7 schematically represents a cross-sectional view of a permanentmagnet module according to one example of the present disclosure;

FIG. 8 shows a flow diagram of an example according to the presentdisclosure of a method for removing an electromagnetic module from anelectrical machine;

FIG. 9 shows a flow diagram of an example according to the presentdisclosure of a method for removing a stator segment from a stator.

FIG. 10 shows a flow diagram of an example of a method for inserting anelectromagnetic module to an electrical machine.

DETAILED DESCRIPTION OF EXAMPLES

In these figures the same reference signs have been used to designatematching elements.

FIG. 1 illustrates a perspective view of one example of a wind turbine1. As shown, the wind turbine 1 includes a tower 2 extending from asupport surface 3, a nacelle 4 mounted on the tower 2, and a rotor 5coupled to the nacelle 4. The rotor 5 includes a rotatable hub 6 and atleast one rotor blade 7 coupled to and extending outwardly from the hub6. For example, in the illustrated example, the rotor 5 includes threerotor blades 7. However, in an alternative embodiment, the rotor 5 mayinclude more or less than three rotor blades 7. Each rotor blade 7 maybe spaced from the hub 6 to facilitate rotating the rotor 5 to enablekinetic energy to be transferred from the wind into usable mechanicalenergy, and subsequently, electrical energy. For instance, the hub 6 maybe rotatably coupled to an electric generator 10 (FIG. 2 ) positionedwithin the nacelle 4 or forming part of the nacelle to permit electricalenergy to be produced. The rotation of the rotor may be directlytransmitted, e.g. in direct drive wind turbines, or through the use of agearbox to a generator.

FIG. 2 illustrates a simplified, internal view of one example of anacelle 4 of a direct drive wind turbine 1. As shown, the generator 10may be disposed within the nacelle 4 or between the nacelle 4 and therotor 5. In general, the generator 10 may be coupled to the rotor 5 ofthe wind turbine 1 for generating electrical power from the rotationalenergy generated by the rotor 5. For example, the rotor 5 of the windturbine may include a hub 6 coupled to a rotor 20 of a generator 10 forrotation therewith. The rotation of the hub 6 may thus drive the rotor20 of the generator 10.

In FIG. 2 , the wind turbine rotor 5 may be rotatably mounted on asupport frame 9 through two rotor bearings 8. In other examples, thesupport frame 9 may not extend through the hub 6 and therefore the rotormay be supported by a single rotor bearing 8, commonly called as themain bearing.

The generator 10 may be electrically coupled to the converter. The windturbine converter may adapt the output electrical power of the generatorto the requirements of the electrical grid.

The generator 10 may comprise a rotor 20 and a stator 30. In FIG. 2 ,the stator 30 is surrounding the rotor 20, however, in other examples,the rotor may surround the stator. Between the stator 30 and the rotor20 an air gap 40 is arranged. The stator may be rigidly mounted on thesupport frame 9. The rotor may be rotatably mounted on the statorthrough a generator bearing 11 so that the rotor may rotate with respectto the stator about a rotational axis. The rotor may extend from a firstside, e.g. from inside the nacelle 4, to a second side, the wind turbinerotor 5.

FIG. 3 schematically represents a cross-sectional view of two adjacentstator segments according to one example of the present disclosure. Astator segment is an example of an electromagnetic module of anelectrical machine.

The stator segments 35,135 of FIG. 3 comprise a base 50, 150 and a tooth80, 180 protruding from the base 50, 150 which receives a stator winding81, 181. The base 50, 135 comprises a bottom surface 53, 153 and a firstside surface 51, 151 having an axially extending groove 60, 160. Theaxially extending groove 60, 160 comprises an upper surface and a lowersurface. In this example, the upper surfaces and the lower surfaces ofthe grooves are substantially flat.

The first side 51 of the stator segment 35 faces the first side 151 ofthe stator segment 135. The grooves 60 and 160 form a cooling channel70. The cooling channel 70 is configured to receive a rod for removingone of the stator segments from a stator rim 31. The cooling channel 70is further configured to remove heat from the stator windings 81 and181. In some examples, the cooling channel 70 is further configured toreceive a rod for inserting a stator segment in an electrical machine.

The upper surface and the lower surface of the grooves of this figureare substantially parallel to each other. The upper surface and thelower surface may extend substantially perpendicular to the first sidesurface. In this example, the cooling channel 70 has a substantiallyrectangular shape.

In this example, the stator segments 35,135 further comprise a secondside surface 52, 152 comprising an axially extending groove 60, 160having an upper surface and a lower surface. The groove arranged at thefirst side surface may be similar to the groove of the second sidesurface.

The teeth 80, 180 of FIG. 3 extend substantially perpendicular to thebottom surface 53, 153 of the base. In this example, the first 51, 151and the second side surfaces 52, 152 are substantially parallel to eachother. In addition, these side surfaces are substantially perpendicularto the bottom surface 53, 153.

A rod may be held or retained between the upper surface and the lowersurfaces of a groove. The upper surface of the groove may contact anupper surface of a rod inserted in the cooling channel. The uppersurface of the groove may thus limit a radial movement of the rod insidethe cooling channel. Similarly, the lower surface of the groove maycontact a lower surface of a rod inserted in the cooling channel tolimit a radial movement of the rod.

A half portion of the upper surface and a half portion of the lowersurface of the rod may respectively contact the upper and lower surfacesof the one of the grooves. One half portion of the rod may besubstantially held by one of the grooves, whereas the other half portionof the rod may be substantially retained by the other groove thatdefines the cooling channel.

In this example, the stator segments 35, 135 are connected to a statorrim 31 through a fastener or a plurality of fasteners. Particularly, thebase comprises an axial recess 58, 158 receiving an anchor 22, 122. Theanchor 22, 122 may fit the shape of the recess 58, 158 to maintain thestator segment in place. The anchor may comprise a threaded hole atwhich a fastener or a bolt 23, 123 may be screwed to connect the anchor22, 122 to the stator rim 31. The bolt 23,123 may pass through a radialhole provided on the stator rim 31 to fix the stator segment to thestator rim. The anchor may thus be tightened to press the stator segmentagainst the stator rim.

In some examples, the anchor may comprise a plurality of threaded holesdistributed along its length to receive a plurality of bolts passingthrough a plurality of holes arranged at the stator rim. A plurality ofconnections may thus be stablished between the stator segments and thestator rim.

The anchor 22,122 of the FIG. 3 is substantially T-shaped. In otherexamples, the anchors may be of a suitable shape to fit a recess of thebase of the stator segment.

In other examples, a fastener or a plurality of fasteners may directlyconnect the stator segment to the stator rim.

In the example of FIG. 3 , the stator module comprises a single toothreceiving a stator winding. However, in other examples, the statormodule may comprise a plurality of teeth. These teeth may receive astator winding. For example, the stator module may comprise 2 or 3teeth. A stator winding may be wounded in each of the teeth.

FIG. 4 schematically represents removing one of the stator segments ofFIG. 3 from a stator.

In this figure, a rod 90 is inserted in the cooling channel 70 formed bythe groove 60 and the groove 160. The rod may axially slide along thecooling channel. The rod may thus be moved along a directionsubstantially parallel to its length. The stator segment 35 may beremoved from the stator by sliding it along the rod 90. In this figure,the stator segment 135 is connected to the stator rim whereas the statorsegment 35 has been released from the stator rim. For clarity purposes,the connection of the stator segments to the stator rim and a recess forreceiving an anchor have not been illustrated in this figure. However,the stator segments may be connected to the stator rim according to anyof the examples herein described.

As the stator segment is attached to the stator rim, the groove 160 ofthe stator segment 135 may retain the rod 90 in place. The upper andlower surfaces of the groove 160 may respectively contact a portion ofthe upper and lower surfaces of the rod to hold the rod. As a result,the rod may also limit the radial movement of the stator segment 35being removed or inserted. Attraction forces created by the permanentmagnets towards the stator module being removed or inserted may thus becounteracted. For example, the upper surfaces of the grooves and theupper surface of the rod may be flat. This may also be for the lowersurfaces of the groove and the lower surface of the rod.

A portion of the rod may be retained inside the grove 160 of the statorsegment 135 (fixed to stator rim). An additional tool may be connectedto the rod to prevent an undesirable axial movement of the rod, i.e. toprevent a movement of the rod along its length.

The cross-section of the rod may have a cross-section similar to thecross-section of the cooling channel. In FIG. 4 , the rod 90 has asubstantially rectangular cross-sectional shape, like the coolingchannel 70. Other shapes of rods and cooling channels may also besuitable. In these examples, the rod may substantially engage thecooling channel.

FIG. 5 schematically represents a cross-sectional view of a statorsegment according to one example of the present disclosure.

The stator segment 35 of FIG. 5 comprises a base 50 and a tooth 80protruding from the base 50, which receives a stator winding 81. Thebase 35 comprises a bottom surface 53 and a first side surface 51 and asecond side surface 52. In this example, the first 51 and the secondside surfaces 52 comprise an axially extending groove 60. The axiallyextending grooves 60 comprise an upper surface 61 and a lower surface62. The upper surface 61 and the lower surface of this figure are flatand substantially perpendicular to the first side surface 51 and to thesecond side surface 52.

In this example, the grooves further comprise an inner surface 63connecting the upper surface 61 to the lower surface 62. The innersurface 63 may be substantially flat and may extend substantiallyperpendicular to the upper surface 61 and to the lower surface 62. Thegrooves may thus have a rectangular or square cross-sectional shape. Insome examples, a transition between the surfaces of the groove may berounded. Magnetic lines fluxing from one stator segment to an adjacentstator segment may have a smoother transition around the coolingchannel.

A cooling channel may be formed by the groove 60 of the first side 51 ofthe stator segment of this figure and a groove a first side of anadjacent or a neighboring stator segment (not illustrated in FIG. 5 ).The cooling channel may have a rectangular cross-sectional shape. Therod may thus have a rectangular or square shape to fit the coolingchannel.

The first side surface 51 of this figure comprises a first 511 and asecond portion 512. The grove 60 of the first side surface 51 may bearranged between the first 511 and the second portion 512. The secondportion 512 may extend from the base 53 to the lower surface 62 of thegroove 60. The first portion 511 may extend from the upper surface 61 toa first support surface 54. The groove 60 of the first side surface 51may thus be arranged relatively close to the electrical winding 81 to becooled.

In some examples, a length of the second portion 512 may be longer thana length of the first portion 511. A length of the second portion refersto a distance between the bottom surface 53 and the lower surface 62 ofthe groove 60. A length of the first portion refers to a distancebetween the lower surface 61 of the groove 60 and the first supportsurface 54 at which the electrical windings may rest on.

Like described with respect to the first side surface 51, the secondside surface 52 may also comprise a first 521 and a second portion 522.The groove 60 may be arranged between the first 521 and the secondportion 522. And for example, the length of the second portion 522 maybe longer than the length of the first portion 512.

In some examples, the length of the first portions 511, 521 may belonger or equal than the length of the second portions 512, 522.

The base may comprise a first support surface 54 connecting the firstside surface 51 to the tooth 80 and a second support surface 55extending from the second side surface 52 to the tooth. The supportsurfaces may connect the first portions of the side surfaces to thetooth, wherein the support surfaces may contact the stator winding. Thestator winding 81 may be wounded around the tooth 80 and may abutagainst the first support surface 54 and against the second supportsurface 55. The support surfaces may be substantially parallel to thebottom portion 53 and substantially perpendicular to the side surfaces.

The bottom surface 53 of this example comprises a central recess 58 toreceive an anchor 22 to fix the stator segment to a stator rim. Inparticular, the anchor of FIG. 5 may be according to the anchor of FIG.3 . In other examples, other fixing systems may also be suitable.

The base 50 may comprise additional cooling channels. In FIG. 5 , theseadditional cooling channels 71 are formed on the bottom surface 53 ofthe base 50. However, these additional cooling channels are more faraway from the stator windings and from the air gap of the electricalmachine than the cooling channels defined by the grooves of the firstsides of two adjacent stator segments. The cooling effect is thereforeenhanced by the cooling channels formed between two neighboring statorsegments.

FIG. 6 schematically represents a cross-sectional view of a statorsegment according to another example of the present disclosure. Thestator segment 35 of FIG. 6 is similar to the stator segment illustratedin FIG. 5 , however the groove has a different shape. The grooves of thestator segment of FIG. 6 have a substantially wedge shape. The grooves60 of this figure comprise an upper surface 61 and a lower surface 62.The upper surface 61 may be parallel to the lower surface 62. Theseupper and lower surfaces may be flat and substantially perpendicular tothe first lateral side 51 and to the second lateral side 52. Inaddition, the grooves of this figure comprise an inner surface 63 and aninclined surface 64. The inner surface and the inclined surface of thisfigure are substantially flat.

The inner surface 63 may extend from the upper surface 61 to theinclined surface 64. The inner surface 63 may extend substantiallyperpendicular to the upper surface 61. The inclined surface 64 mayextend from the inner surface 63 to the lower surface 62. The inclinedsurface 64 may form an angle higher than 90° with respect to the innersurface 63 and with the lower surface 64. Distribution of magnetic linesfluxing from one stator segment to an adjacent stator segment may beimproved as the magnetic lines around the cooling channel may have asmooth transition. Electrical losses of the electrical machine, e.g. awind turbine generator, may thus be reduced. In some examples, edgesbetween the flat surfaces of the groove may be rounded. Distribution ofthe flux density may be further improved.

A stator of a wind turbine generator may comprise a plurality of statorsegments according to any of the examples herein disclosed.Specifically, a direct-drive wind turbine generator may comprise astator supporting a plurality of stator segments according to any of theexamples herein disclosed.

FIG. 7 schematically represents a cross-sectional view of a permanentmagnet module 25 according to one example of the present disclosure. Apermanent magnet module is an example of an electromagnetic module of anelectrical machine.

The permanent magnet module 25 of FIG. 7 comprises a base 50 and asupport 80 extending from the base 50 supporting at least one permanentmagnet 82. The base comprises a bottom surface 53 and a first sidesurface 51. The first side surface 51 comprises an axially extendinggroove 60 defining a cooling channel with an axially extending groove ofa first side surface of an adjacent permanent magnet module.

In this example, the base 50 further comprises a second side surface 52having a groove which may define a cooling channel with a groove of sidesurface of an adjacent permanent magnet module.

In this example, the permanent magnets 82 are retained inside axialapertures perforated between the base 50 and the support 80. The support80 may be a flux concentrator. In this example, the permanent magnetshave a V-shape configuration. The permanent magnets may thus beoutwardly inclined.

In some examples, the support may be adjustable connected to the base toclamp a pair of permanent magnets in between. In further examples,permanent magnets may also be arranged in a flat configuration.

In the example of FIG. 7 , the support 80 comprises an axial hole 88 toreceive an anchor 22. In this example, the axial hole 88 and the anchor22 has a substantially circular cross-sectional shape. A bolt 23 maypass through a radial hole of the rotor rim 21 to be connected theanchor 22. The bolt 23 may be screwed onto a threaded hole of the anchor22. In some examples, a plurality of bolts may be screwed onto aplurality of threaded holes of the anchor 22.

In other examples, the anchor may have a different shape. For example,the anchor may have a rectangular shape or a T-shape. The axial hole maythus have a similar shape.

In further examples, the axial hole to receive the anchor may bearranged on the base. The base may comprise a recess and the permanentmagnet module may be attached to the rotor rim with an anchor accordingto any of the examples herein disclosed with respect to stator windingsconnected to the stator rim.

The grooves of FIG. 7 comprise a parallel flat upper and a lower surfaceas described with respect to the examples of grooves of stator segments.In this respect, the groove may be according to any of the examplesherein described.

The permanent magnet of this figure may be removed from a rotor orinserted in a rotor using a rod as described with respect to theexamples of removing a stator segment.

A wind turbine generator may comprise a plurality of permanent magnetmodules according to any of the examples herein disclosed. The windturbine generator may be a direct drive wind turbine generator. The windturbine generator may also comprise a plurality of stator segmentsaccording to any of the examples herein disclosed.

FIG. 8 shows a flow diagram of an example according to the presentdisclosure of a method 100 for removing an electromagnetic module froman electrical machine.

The electrical machine comprises a rotor and a stator. Furthermore, theelectrical machine comprises a plurality of electromagnetic modulesconnected to a structure of the electrical machine. In some examples,the structure of the electrical machine may comprise a stator rim or arotor rim. The electromagnetic module may be a stator segment orpermanent magnet module according to any of the examples hereindisclosed.

The electromagnetic module comprises a base and a support extending fromthe base supporting an electromagnetic material. The electromagneticmaterial may be one of a permanent magnet and a stator winding. Theelectromagnetic module comprising a permanent magnet may be a permanentmagnet module. The electromagnetic module comprising a stator windingmay be a stator segment.

The base of the electromagnetic module comprises a bottom surface and afirst side surface. The first side surface comprises an axiallyextending groove defining a cooling channel with an axially extendinggroove of a first side surface of an adjacent electromagnetic module.

At block 101, inserting a rod in the cooling channel formed by thegroove of the electromagnetic module to be removed and the groove of theadjacent electromagnetic module is provided. The rod may thus beretained inside the cooling channel.

The rod may engage the cooling channel. The groove forming the coolingchannel may comprise an upper and a lower surface extendingsubstantially perpendicular to the first side surface. The rod maycomprise two surfaces configured to rest on the upper surface and on thelower surface of the grooves forming the cooling channel. The upper andlower surfaces of the rod and the grooves may be substantially flat.

Releasing the electromagnetic module to be removed from the structure ofthe electrical machine is represented at block 102. The electromagneticmodule to be removed may be attached to the stator rim or to the rotorrim according to any of the examples herein described.

In some examples, releasing or disconnecting the electromagnetic moduleto be removed may comprise loosening fasteners connecting theelectromagnetic module to the structure of the electrical machine. Insome examples, these fasteners may be bolts connecting the structure ofthe electrical machine to an anchor arranged on a recess or a hole ofthe electromagnetic module.

A rod inserted inside the cooling channel formed between theelectromagnetic module to be removed and the adjacent electromagneticmodule may retain a radial movement of the electromagnetic module to beremoved.

The method may further comprises retaining the rod inside the groove ofthe adjacent stator segment, which is fixed to the structure of theelectrical machine. For example, an additional tool may prevent an axialmovement of the rod along the groove. This may help to facilitateremoving the electromagnetic module to be removed.

At block 103, sliding the electromagnetic module to be removed along therod is represented. The electromagnetic module may axially slide and therod may maintain the radial position of the electromagnetic module. Forexample, if the electromagnetic module is a stator segment, the distancebetween the stator segment sliding along the rod and the permanentmagnets arranged on the rotor may thus be maintained. Accordingly,electromagnetic forces attracting or repelling the electromagneticmodules may be counteracted.

FIG. 9 shows a flow diagram of an example according to the presentdisclosure of a method 110 for removing a stator segment from a stator.

The stator comprises a plurality of stator segments connected to astator rim. The stator segments may be according to any of the examplesherein disclosed.

The stator segments may comprise a base and a tooth protruding from thebase and supporting a stator winding. The base may comprise a bottomsurface to contact the stator rim and a first side surface. The firstside surface may comprise an axially extending groove. This groove mayform a cooling channel with an axially extending groove of a first sidesurface of an adjacent stator segment.

In some examples, the groove may be arranged between a first and asecond portions of the first side surface. In some examples, the statorsegments may further comprise a second side surface having a groove.

The groove may be according to any of the examples herein disclosed. Forexample, the groove may comprise a flat upper surface and a flat lowersurface. These surfaces may extend perpendicular to the first sidesurface.

The groove may further comprise an inner surface and an inclinedsurface. The inner and the inclined surfaces may be substantially flat.The inner surface may extend from the upper surface to the inclinedsurface. The inclined surface may connect the inner surface to the lowersurface. The inclined surface may form an angle higher than 90° withrespect to the inner surface and to lower surface. In some examples, atransition between flat surfaces of the groove may rounded. With theseshapes, magnetic lines fluxing through the base may be guided around thecooling channel in a smooth way, reducing magnetic losses.

At block 111, inserting a rod in the cooling channel formed by thegroove of the stator segment to be removed and the groove of theadjacent stator segment is provided. The rod may axially slide along thecooling channel. The rod may thus be retained inside the coolingchannel. An upper or a lower surface of the rod may contact the upper orthe lower surfaces of the grooves forming the cooling channel. Thesesurfaces may be substantially flat. The rod may thus be retained insidethe cooling channel. The rod may have a shape substantially similarshape to the cross-section of the cooling channel.

Block 112 represents releasing the stator segment to be removed from thestator segment. This may comprise loosening fasteners connecting thestator segment to the stator rim. The stator segment to be removed maybe connected to the stator rim according to any of the examples hereindisclosed.

Block 113 represents sliding the stator segment to be removed along therod. The rod is retained by the groove of the adjacent stator segment.The stator segment is prevented from being moved towards the permanentmagnet modules of the rotor. The rod may be retained inside the grooveof the adjacent stator segment to prevent sliding together with thestator segment being removed.

FIG. 10 shows a flow diagram of an example of a method 200 for insertingan electromagnetic module to an electrical machine.

The electrical machine comprises a rotor and a stator. Furthermore, theelectrical machine comprises a plurality of electromagnetic modulesconnected to a structure of the electrical machine. The electromagneticmodules may be according to any of the examples herein disclosed. Insome examples, the structure of the electrical machine may comprise astator rim or a rotor rim. The electromagnetic module may be a statorsegment or permanent magnet module according to any of the examplesherein disclosed.

The base of the electromagnetic module comprises a bottom surface and afirst side surface. The first side surface comprises an axiallyextending groove defining a cooling channel with an axially extendinggroove of a first side surface of an adjacent electromagnetic module.

At block 201, inserting a rod in the groove of an electromagnetic moduleattached to a structure of the electrical machine. The rod may thus beretained inside the groove of this electromagnetic module.

Inserting a portion of the rod in a portion of the groove of theelectromagnetic module to be inserted is represented at block 202. Theelectromagnetic module may be positioned close to the electrical machinesuch that to groove can receive a portion of the rod.

At block 203, sliding the electromagnetic module to be inserted alongthe rod to position the electromagnetic module to be inserted adjacentto the electromagnetic module attached to the structure of theelectrical machine. The electromagnetic module may axially slide alongthe rod. The rod may thus radially retain the electromagnetic modulebeing inserted.

At block 204, the electromagnetic module is attached to the structure ofthe electrical machine. In this way, after positioning theelectromagnetic module by sliding it along the rod, the electromagneticmodule may be attached to the structure of the electrical machine. Theelectromagnetic module may be attached to the electrical machineaccording to any of the examples herein described.

After securing the electromagnetic module to the structure of theelectrical machine, the rod may be removed.

In some examples, the electromagnetic module may comprise a statorsegment with at least one stator winding and the structure of theelectrical machine may comprise a stator rim of the stator. In otherexamples, the electromagnetic module may comprise a permanent magnetmodule and the structure of the electrical machine may comprise a rotorrim of the rotor.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal languages of the claims.Aspects from the various embodiments described, as well as other knownequivalents for each such aspects, can be mixed and matched by one ofordinary skill in the art to construct additional embodiments andtechniques in accordance with principles of this application. Ifreference signs related to drawings are placed in parentheses in aclaim, they are solely for attempting to increase the intelligibility ofthe claim, and shall not be construed as limiting the scope of theclaim.

1. An electrical machine having a rotor and a stator, the electricalmachine comprising: a plurality of electromagnetic modules having anelectromagnetic material, the electromagnetic material being one of apermanent magnet or a stator winding, each of the electromagneticmodules comprising: a base and a support extending from the base andsupporting the electromagnetic material, the base comprising: a bottomsurface; a first side surface and a second side surface, one or both ofthe first and second side surfaces comprising an axially extendingopen-sided groove; and wherein the open-sided groove mates with theopen-sided groove of an adjacent electromagnetic module to define aclosed-sided cooling channel.
 2. The electrical machine according toclaim 1, further comprising a rod insertable into the cooling channeland having a length such that one of the electromagnetic modules isslidable along the rod for removal from the electrical machine.
 3. Theelectrical machine according to claim 2, wherein the electromagneticmodule to be removed comprises a rotor rim segment having a permanentmagnet module with at least one permanent magnet.
 4. The electricalmachine according to claim 2, wherein the electromagnetic module to beremoved comprises a stator rim segment having at least one statorwinding.
 5. The electrical machine according to claim 1, furthercomprising releasable fasteners connecting the electromagnetic modulesto the electrical machine.
 6. The electrical machine according to claim1, wherein the open-sided groove in the first or second side surface ofthe electromagnetic module comprises an upper and a lower surfaceextending substantially perpendicular to the respective first or secondside surface.
 7. The electrical machine according to claim 6, whereinthe upper and lower surface are parallel to each other.
 8. Theelectrical machine according to claim 6, wherein the open-sided groovecomprises an inner surface and an inclined surface, the inner surfaceextending perpendicular from the upper surface to the inclined surfaceand the inclined surface extending from the inner surface to the lowersurface, wherein the inclined surface forms an angle greater than 90°with respect to the inner surface and with the lower surface.
 9. Theelectrical machine according to claim 8, wherein the surfaces of theopen-side groove are substantially flat and a transition between thesurfaces of the groove is rounded.
 10. A stator segment for anelectrical machine, comprising: a base and a tooth protruding from thebase, the tooth supporting a stator winding; the base comprising: abottom surface; a first side surface and a second side surface, one orboth of the first and second side surfaces comprising an axiallyextending open-sided groove; and wherein the open-sided groove isconfigured to mate with the open-sided groove of an adjacent statorsegment to define a closed-sided cooling channel.
 11. The stator segmentaccording to claim 10, wherein the open-sided groove in the first orsecond side surface comprises an upper and a lower surface extendingsubstantially perpendicular to the respective first or second sidesurface.
 12. The stator segment according to claim 11, wherein the upperand lower surface are parallel to each other.
 13. The stator segmentaccording to claim 12, wherein the open-sided groove comprises an innersurface and an inclined surface, the inner surface extendingperpendicular from the upper surface to the inclined surface and theinclined surface extending from the inner surface to the lower surface,wherein the inclined surface forms an angle greater than 90° withrespect to the inner surface and with the lower surface.
 14. The statorsegment according to claim 13, wherein the surfaces of the open-sidegroove are substantially flat and a transition between the surfaces ofthe open-side groove is rounded.
 15. The stator segment according toclaim 10, wherein the open-sided groove is configured for slidingreceipt of a rod therein such that the stator segment is removable froman electrical machine by sliding along the rod.